This invention relates to a new class of organic compounds and polymers derived from them. More particularly, it relates to new bis-anhydrides derived from trimellitic anhydride, a method for their preparation and polymers made by copolymerizing them with diamines or diols. These compositions contain two anhydride groups, an azo (-N=N-) structure as well as a residue contributed by the organic ketone reaction medium. Specifically, our invention provides bis-anhydrides having the general formula: ##STR2## wherein R.sub.1 and R.sub.2 are alkyl radicals of up to 6 carbon atoms, halogenated alkyl radicals of up to 6 carbon atoms or phenyl radicals.
As a result of the existence of two reactive anhydride groups per molecule which can readily undergo reactions well known to the art, e.g. reactions with glycols, polyols, diamines, epoxides and the like, the compounds of our invention are useful in the preparation of a variety of resinous materials. They can undergo copolymerization forming such polymers as polyesters, polyamides and polyimides. Further, the presence of the azo group, a well known chromophore group, leads to a colored or dyed product. Additionally, the incorporation of the solvent molecule (ketone residue) adjacent to the azo group leads to greater selection and control of the chemical environment near the chromophore group and hence the color. These compounds are also useful in grafting on to pre-existing polymeric molecules and promoting crosslinking as well as dyeability.